Yes. Sign Language is speech.
Rhetorical Critics will tell you that anything is “speech” if the purpose is to convey a message. That includes things like architecture, art, clothing, or no clothing. Certainly women who go topless are attempting to convey a message. Trying to figure out what that message is can be problematic. The next question is “is this protected speech”. My take is that the Founders were protecting political speech. So unless these women are running for office on a platform of [insert joke here] it’s not constitutionally protected speech. IMHO
You posted, in part: Certainly women who go topless are attempting to convey a message. Trying to figure out what that message is can be problematic.
That is where I don’t get it. Speech means communication, doesn’t it? If the message can’t be discerned, how is that speech? This is the same problem I have with flag burning as speech. What does burning the American flag mean? “I hate America?... I hate the current administration?... I hate Congress?... I hate the American way of life?... etc., etc.” If the expression is devoid of any real meaning discernable to the average “listener” how is that speech in any real way?
As for seeing women topless, I find it hard (no pun intended) to object, as long is the woman is not my wife or daughter. If the woman is unattractive one can look away. As the comedian Ron White says: Once you seen one woman’s [breasts] you pretty much want to see them all.